For example, Patent Literature 1 discloses a measuring apparatus for measuring an expansion coefficient or the like of a sample whose expansion coefficient or contraction coefficient is unclear, based on an amount of change of the sample at a predetermined temperature. This measuring apparatus sets a temperature of a sample to be a predetermined temperature, and measures the expansion coefficient or the like of the above-mentioned sample based on image data in a transmitted light quantity of a lens positioned at a predetermined position.
Furthermore, Patent Literature 2 describes a tool observing method comprising imaging, using a camera, a cutting tool such as a tool bit (hereinafter, also referred to as tool) for cutting a workpiece which is an object to be processed, and observing the tool for any breakage, wear or the like based on image data thereof, wherein at least either before or after processing the object to be processed, a tool is rotated or moved so as to capture multiple pieces of image data thereof, and the tool is observed for any breakage, wear or the like using image data in focus which is selected from the multiple pieces of image data. Furthermore, Patent Literature 3 discloses a system for automatically inspecting a tool chip of a machine tool for any wear or the like using a visual sensor. This system illuminates a slit on a chip from an illuminating window of a structure light unit, and shoots with a camera through an imaging window, thereby automatically inspecting the tool chip for any wear or the like.